The present disclosure relates to a method providing a heat mode for an exhaust gas after treatment device in a vehicle, such as for regenerating an exhaust gas particulate filter in the exhaust gas after treatment device, the vehicle comprising an internal combustion engine, an electric machine, a transmission, and a clutch connecting the internal combustion engine to the transmission and driving wheels. The present disclosure also relates to a vehicle, a computer program, a computer readable medium and a control unit.
All vehicles, and in particular heavy duty trucks and buses, which have a hybrid driveline are generally provided with an internal combustion engine which does not suffice for all driving conditions of the vehicle. Instead an electric machine is added which used to support the internal combustion engine, or even singlehandedly drive the vehicle during certain driving conditions. The latter is particularly beneficial at times when low fuel consumption is sought, when low or no exhaust emissions are wanted, or when low noise levels are advantageous. The electric machine is not only operating as a vehicle driving machine, but is also operating as a generator, although at different occasions. It may thus deliver energy when there is an energy surplus to an energy storage, normally batteries, or to a super condenser or a flywheel for later use.
Many modern vehicles of these kinds are provided with an exhaust gas after treatment system (EATS). Especially heavy duty trucks and buses running on diesel fuel have such systems in order to meet emission regulations in different legislations. For these exhaust gas after treatment systems to function properly the fuel has to meet certain contents criteria, and the temperature of the system or of parts thereof have to be within certain limits, usually high enough to perform appropriately. A difficulty with regard to a hybrid driveline in particular in a driveline having a diesel internal combustion engine together with an electric machine, is that the exhaust gases which are resulting from the combustion of diesel fuel in the internal combustion engine may enter the exhaust gas after treatment system having a temperature which is too low to keep the exhaust gas after treatment system at a suitable temperature.
One part of such an exhaust gas after treatment system is a diesel particulate filter (DPF). During use of the filter emissions such as soot and particulates from the exhaust gases are collecting in the filter. The filter will over time lose its capacity to collect more particulates unless it is cleaned through intermittent regeneration. Detecting a need for DPF regeneration is often made through a pressure difference measurement between the outlet and the inlet of the filter. Regeneration may be achieved by increasing the temperature of the filter to such an extent that self-combustion of the particulates takes place. When it has been established that regeneration of the DPF is needed this can be achieved either at vehicle still stand or during driving. For initiation of the self-combustion external heating additional to the heat comprised in the exhaust gases may sometimes be required, but during regeneration such additional heating may be less needed since the heat generated by the self-combustion itself may be enough to keep the regeneration going.
One difference in driving conditions between hybrid passenger cars and hybrid heavy duty trucks and busses is that while the passenger car most often is driven such that a comfortable and calm driving style prevails, especially during acceleration, a heavy duty truck or bus instead is designed for applying frill power in order to perform well under similar conditions.
By the terms driving of the vehicle is meant to either start off from a still stand of the vehicle, or the propulsion of the vehicle such that it through possibly discontinuous speed travels a distance in a generally forward direction.
There is a continuous endeavour to improve the drivability and reduce the exhaust emissions from these types of vehicles.
It is desirable to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. It is moreover desirable to further improve the drivability and reduce the emissions from vehicles.
According to a first aspect of the present disclosure a method tier providing a heat mode for an exhaust gas after treatment device the vehicle is disclosed, which vehicle comprises an internal combustion engine, an electric machine, a transmission, and a clutch connecting the internal combustion engine to the transmission and driving wheels. The method comprises the steps of:
establishing that a heat mode for the exhaust gas after treatment device is demanded,
establishing that driving of the vehicle is demanded, and during a period when the clutch is at least partially decoupling the transmission, providing at least a predominant part of a required driving torque to the driving wheels by the internal combustion engine, such that exhaust gases from the internal combustion engine are heating the exhaust gas after treatment device.
By performing this method it has surprisingly been found that the temperature of the exhaust gases are increased to such an extent that a heat mode for the exhaust gas after treatment device may be achieved without undue additional heating of either the exhaust gases or of the exhaust gas after treatment device, where it otherwise would not have been possible. Additional heating of e.g. the exhaust gases may still be either needed or necessary, but this additional heating is at least reduced in comparison to known methods. This is particularly advantageous for a hybrid heavy duty truck or bus, even more so for a vehicle in commercial traffic, thanks to the commonly known driving manner of providing nearly full or full power. Thanks to the provision of at least a predominant part of the required driving torque to the driving, wheels by the internal combustion engine, the temperature increase may be significant and enough to provide the heat mode when it otherwise would not have been possible. Regeneration of an exhaust gas particulate filter is one embodiment of a heat mode for the exhaust gas after treatment device. Other heat modes may include heating of different embodiments of catalysts included in the exhaust gas after treatment device. The fuel consumption which is needed to provide the predominant part of the required driving torque by the internal combustion engine is at least to a certain extent compensated by the reduction of energy needed for either providing additional heating to the exhaust gas after treatment device. It might otherwise be necessary to for instance run the exhaust gas after treatment device at a lower capacity, or to even stop the vehicle fin providing the heat mode for the exhaust gas after treatment device in some other manner.
According to an embodiment the method is used for regenerating an exhaust gas particulate filter in the exhaust gas after treatment device, and the step of establishing that a heat mode for the exhaust gas after treatment device is demanded includes establishing that regeneration of the exhaust gas particulate filter is demanded, such that exhaust gases from the internal combustion engine are heating the exhaust gas particulate filter for regeneration thereof.
The heat mode is very advantageous for providing a possibility to regenerate an exhaust gas particulate filter, such as a diesel particulate filter. If not regenerating such an exhaust gas particulate filter on either a regular basis, or at occasions when it is found necessary, particulate matter may clog the exhaust gas particulate filter such that ultimately the vehicle would have to stop driving in order to regenerate the exhaust gas particulate filter.
According to an embodiment the step of providing at least a predominant part of the required driving torque to the driving wheels by the internal combustion engine is performed during a closing of the clutch.
Closing of the clutch is generally performed when the engine is reconnected to the driveline. This most often occurs at either taking off from a stillstand, or at repowering of the driving wheels in order to continue driving. During this phase the transmission speed is adapted to the speed of the driving wheels, and for this energy is required. By performing the method according to this embodiment an additional temperature rise may be achieved for the heat mode.
According to an embodiment, when the required driving torque is less than a deliverable driving torque from the internal combustion engine, only providing the required driving torque by the internal combustion engine.
Hereby the effect of temperature rise in the exhaust gas is even more pronounced, since all required driving torque is provided by the internal combustion engine which produces hot exhaust gases that in turn heats the exhaust gas particulate filter.
According to an embodiment, during said clutch decoupling, the method controls the internal combustion engine to provide its maximum, or close to maximum, driving torque.
A more pronounced effect of temperature rise in the exhaust gas after treatment device and possibly the exhaust gas particulate filter is thus achieved since the internal combustion engine is working at or close to peak power.
According to an embodiment, when the required driving torque is greater than a deliverable driving torque from the internal combustion engine, in addition also providing by the electric machine a deficient driving torque in relation to the required driving torque and the deliverable driving torque by the internal combustion engine.
This way the electric machine is only providing driving torque when the internal combustion engine has reached its peak power, or in other words its maximum deliverable driving torque.
According to an embodiment the step of establishing that driving of the vehicle is demanded includes establishing, that a driving torque is demanded from the vehicle.
According to an embodiment the step of establishing that a driving torque is demanded from the vehicle is performed by sensing that an accelerator pedal in the vehicle is being depressed.
This is a simple manner of achieving the desired result of establishing that a driving torque is demanded from the vehicle.
According to an embodiment the step of clutch decoupling involves an adaption of a gear ratio of the transmission.
According to an embodiment the step of adaption of the gear ratio of the transmission is performed during an upshift of the gear ratio.
During an upshift of the gear ratio of the transmission the vehicle is normally accelerating. During, acceleration power is demanded for driving the vehicle, and during such conditions the elect of increasing the temperature of the exhaust gas after treatment device and possibly the exhaust gas particulate filter through hot exhaust gases is most pronounced.
According to an embodiment the step of establishing that regeneration of the exhaust gas particulate filter is demanded is established based on measuring a pressure difference between an outlet and an inlet of the exhaust gas particulate filter.
This is a simple manner and consequently cheap way of establishing that regeneration of the exhaust gas particulate filter is demanded.
According to an embodiment the clutch decoupling is performed during an acceleration phase of the vehicle from standstill.
During an acceleration phase of the vehicle from standstill the longest period for requiring a driving torque from the vehicle can be achieved, and hereby the greatest potential for a heat mode for the exhaust gas after treatment device and possibly a temperature rise in the exhaust gas particulate filter is at hand.
According to an embodiment the clutch decoupling is performed during driving.
According to an embodiment the method is performed by a control unit in the transmission of the vehicle.
By utilizing a control unit in the transmission of the vehicle for performing the method a control unit which is also controlling the clutch is utilized so that a smooth control without competing or even colliding requirements between different control units is achieved.
According to an embodiment the method further comprises the step of performing regeneration of the exhaust gas particulate filter when a temperature of the exhaust gas particulate filter is above a predetermined temperature.
Hereby the best possible performance of the regeneration of the exhaust gas particulate is achieved.
According to an embodiment the method is arranged to be performed in a regeneration mode which satisfies the condition of establishing that regeneration of the exhaust gas particulate filter is demanded, which regeneration mode is arranged to set aside a normal hybrid driving mode, in which normal hybrid driving mode at least a predominant part of the required driving torque to the driving wheels is arranged to be provided by the electric machine.
For a hybrid vehicle of the kind according to the present disclosure it is desirable to utilize a hybrid mode to the largest possible extent. This is hence the normal driving mode for such a vehicle. Such a driving mode includes driving the vehicle by the electric machine. While driving the vehicle by the electric machine no, or at least little, exhaust gases are produced by the internal combustion engine. The internal combustion engine may often even be shut down during this hybrid mode. Hence there will during this driving mode be no or at least only little heating of the exhaust gas after treatment device and possibly the exhaust gas particulate filter. Such a hybrid vehicle is during hybrid mode hence adapted to provide a predominant part of the required driving torque by the electric machine. During, a period of utilizing the present method this is consequently interchanged for a situation in which at least a predominant part of the driving torque is provided by the internal combustion engine. The result consequently becomes that heating of the exhaust gas particulate filter is achieved.
According to a second aspect of the present disclosure a computer program is disclosed which comprises program code means for performing the method steps when said program is run on a computer.
According to a third aspect of the present disclosure a computer readable medium is disclosed which carries a computer program comprising program code means for performing the method steps when said program product is run on a computer.
According to a fourth aspect of the present disclosure a control unit for controlling a clutch is disclosed, the control unit being configured to perform the method steps.
This control unit is preferably the Electronic Control Unit (ECU) of the gearbox. According to a fifth aspect of the present disclosure a vehicle is disclosed which comprises an internal combustion engine, an electric machine, a transmission, driving
wheels and a control unit, wherein the control unit is adapted to perform the method in the vehicle.
The vehicle will be provided with the advantage of utilizing a certain driving period for providing a heat mode for the exhaust gas after treatment device, and possibly for re-generation of the exhaust gas particulate filter for achieving a surprisingly good effect of heating the exhaust gases. This is in more detail explained above in connection with the first aspect of the present disclosure.
According to an embodiment the transmission is an automated type of transmission.
This type of vehicle is mostly best controlled by an automated type of transmission to automatically achieve the desired effects.
According to an embodiment the internal combustion engine is a diesel fuel engine.
Due to the composition of the exhaust gases from a diesel fuel internal combustion engine, an exhaust gas after treatment device including possibly an exhaust gas particulate filter is, or at least will be, required in order to meet exhaust emission regulations in many countries. Due also to the need for bringing such devices up to certain temperatures, such as for regeneration of an exhaust gas particulate filter, the present method is particularly advantageous here for.
According to an embodiment the internal combustion engine is configured to provide a relatively low maximum torque and the electric machine is configured to provide a deficient driving torque in relation to a required driving torque and the deliverable driving torque by the internal combustion engine for achieving proper driving performance.
According to an embodiment the vehicle comprises a powertrain with the following components arranged in series: the internal combustion engine, a clutch, the electric machine and the transmission. Other orders may however be prudent.
According to an embodiment the vehicle is constituted by a bus.
Purely as non-limiting examples, a city bus in commercial traffic usually starts and stops regularly and often and so does a refuse lorry. During these stops and taking offs many occasions for performing the method according to the present disclosure will be provided.